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The Terra Firma Concept: Jitter is Analogue

•   1.  Article Written for Audiophile Society of NSW

•   2.  Terra Firma Player Upgrade Description

•   3.  Other Issues (as they present themselves)

JLTi Terra Firma Multi-Player

AUD $1099.00

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THIS IS ABOUT THE IMPORTANCE OF CLOCKING CD PLAYERS AND DIGITAL PLAYBACK - AND A NEW STANDARD OF PERFORMANCE - HOW TO MAKE DIGITAL SOUND MORE LIKE GOOD VINYL

The following are edited excerpts from an article written for the Audiophile Society of NSW, July 2008 Newsletter:

"Terra Firma" and Why Jitter Is Analogue?

I am excited and I have good reason to be, and so do you. In the last few months there have been some truly significants events that may well redefine digital playback once and for all time.

Some of you may have read March 2008 issue of The Absolute Sound a ground breaking review of the Esoteric G-0Rb "Atomic Clock. If you can get a copy of that issue, it is on Page 124 and very well worth the read. It may well be the most single significant article written in that magazine re digital audio.

This review by Robert Harley is already causing a stir in certain quarters and while the review subject is the Esoteric “Atomic Clock” is USD $15,000 there will not be a great market unless a mass produced low cost version is made and even then it will only be cheaper but NOT cheap. Even so, most mainstream players have no way of getting sync.

“The Esoteric G-0Rb Master Clock Generator rendered a much bigger gain in musical realism that I would have thought possible… It had a liquidity, ease, and naturalness that I’ve never heard before from digital audio reproduction. The hardness in the midrange, the glassy shattering sound on leading-edge transients, and the dynamic constriction were all gone, replaced by a silky smooth yet powerful rendering… more vivid… involving… sounding more like the real thing and less like synthetic recreations.”

He goes on at length that this is beyond any previous expectation he had of what he thought was the limits of CD playback. But is this final great leap going to be beyond us Average Joes?

How Long Will It Take To Save $15.000?

But unconsciously Harley is pointing to another solution. While the sonic improvement is beyond question (I know because I and now others recognise they have heard the Holy Grail of digital clocking) he states that this Rubidium clock is power supply insensitive:

"Most other digital audio employ a voltage controlled crystal oscillator [VCXO]... Because the VCXO’s output frequency is a function of the voltage across it, any ripple or variations in the power supply will cause the frequency to change - the very definition of jitter... A Rubidium clock is not only more precise and stable than a VCXO; it is not subject to such variability in its output frequency."

(BTW, not all oscillators are really VCXOs, but Harley seems to use it as a generic description for powered oscillators rather than cheap crystal oscillators.)

Ahah! So the Rubidium clock is insensitive to power supply and oscillators are highly sensitive. If your player has a decent clock, it will be a powered oscillator. But does that mean that our oscillators  should all be thrown into the trash can? Far from doing that, realise the Achilles Heel may not the oscillator itself but the power supply that it is connected to. And this is something we are specialists in. So is there another way to get ‘Atomic’ quality clocking?

If we can stabilise the VCXO's power supply, extreme stability, then the performance of our more common garden oscillator (relative to Atomic Clocks) will take on a level of performance that will simply take your breath away.

How to Get Extreme Stability?

Harley talks about stability, he gets the point. This is surely the antidote to jitter. Our clock power supply needs to be as stable as the very ground we walk on; hence may I introduce you to the concept of Terra Firma. The earth is the biggest rock we can access and hence it has the greatest physical stability available. In the physical world, anything that moves will generally move in cycles. The equivalent electrical concept is AC. The earth, relative to our position in the physical world is DC. Now that is stability and this is our ultimate aim.

Some who work in various labs are familiar with heavy duty anti-vibration tables that are spiked to the ground - so tests can be performed that are not influenced by vibrations.

Is this perfect? No, but the aim is to be as stable as the very ground it sits on, DC like and expulse AC like movement. In above case the table sits on steel enforced concrete slab set into compacted rock hard soil soil (often clay). The actual platform I have seen is a synthetic and extraordinary dense granite. In some cases there will be an anti-tuning device fitted under the platform or part of the frame. This is suitable for high powered microscopes. A commercial version designed for microscopes may look like this:

Can we make a power supply so rock like stable that it has the stability of our mother planet Terra Firma?

No, we cannot achieve it perfectly, but what we can produce is a power supply that has extreme stability in a way that has not been done before. Just as the Atomic Clock is one way to achieve this extreme result, we now have a much more inexpensive solution that may well be proven even superior.

We can now look at CD and digital playback in an entire new light. I was among those back in 1983 that heard first generation players and it was quite horrible. There have been generational improvements along the way - not so much the technology persé but also the implementation of it. I say this because the now obsolete Philips TDA1541A came out in the second half of the 80's and is arguably the most brilliant DAC ever. So why did they not sound that good back then (in fact they still sounded better than much of the pack). The best DAC I have heard is a modern implementation of a 1541A DAC, capable of superb analogue like sounds today. Clock it right, get the fundamentals right too and it is pure magic. Only now are we getting a handle on what jitter really does. We hear it when it is banished.

Back to Harley: In his sidebar article on the History of Jitter he points out the disbelief by much of the Audio Engineering Society that bits were not just bits. The notion of jitter was considered lunacy - you had the credibility of necrophiles and paedophiles (I kid you not) and if you believed in it you were plainly a dangerous person.

"Put an analog signal down a wire, it degrades... not to mention subjecting the signal to every other component in the signal path... audiophiles noticed musically different variations between coaxial and Toslink connections, brands of digital cables - how could the sound change? What mysterious "X" factor that caused [proven] identical digital bitstreams to exhibit an analog-like variability."

That last phrase "analog-like variability" is indeed highly significant. Making physical changes to, not just cables, but other things that deal with the digital datastream - without loosing data - had an "analog-like variability" when converted to analogue and clearly audible. Hence seeming digital changes made for analogue like changes. Digital was not supposed to behave this way – bits were supposed to be bits, no matter what.

 You see: Jitter is Analogue!!!

No, surely not! We think of jitter as a digital artefact, but quite plainly it is not (quantisation error is, but that is another subject). But it is oh so easy to prove. Back in the early days of CDs we noted that the laser pickup's output was a waveform, an analogue waveform (sorry, but I insist on spelling analogue correctly). In fact, you can display it on an analogue oscilloscope - there it is, right on a screen, "looking at you kid" (sorry Bogie).

Harley has previously pointed out that if your datastreams are identical, that is "zero for zero" and "one for one" throughout the stream, the classic binary code, then you have 100% data retrieval. If then these datastreams are converted and clearly sound different, it isn't some error correction but something below the level of that datastream. He then correctly made the conclusion, it can only be jitter.

 Jitter is “Sub Data Error”

Digital is the content, but analogue is the carrier or the form, the actual structure that propels the data. While digital exist as content alone, on your disk or music server hard drive, there is no jitter as such. But once it in motion it consists of a waveform, voltage, current, noise floor and full spectral content, it is all analogue in behaviour.

It is remarkable that we can now conclude that the error inherent in digital is all analogue, the content (program) is digital, the error content (jitter) is analogue.

While we exist in a Digital Age, the environment that surrounds us, the physical world, is all analogue. When digital data (the content) has to be processed, it comes into an analogue world. The digital content is now a stream and is at the mercy of an analogue world. The content is maintained, but below the content the analogue world will put its own footprint. And it is far more audible than we ever imagined.

In fact we are only really now, 25 years after the emergence of CD playback, become aware just how much jitter matters, as Harley concurs in his article.

For many years I have been witnessed by countless number of persons, saying that Low Frequency Jitter is the worst and most audible of all. I have stated ad nauseum  that power supply noise is the source of this worst kind of jitter and the noise floor should remain ultra-low down even to well under Sub One Hertz. Unfortunately, linear cum analogue circuits have by nature rising noise below 100 Hertz, just look at any published graph of any opamp and amplifier or power supply, there is a rise in both voltage and current noise, even the single humble transistor does this.

This is typical of all analogue circuits, in this case the highly acclaimed low noise LM4562 now used by DEQX, Hypex and others. In fact, the above is above average and most are much worse again. As for batteries, they too are entirely inadequate. We have known that analogue noise is the enemy of all digital circuits since about 2003. Now we are learning exactly to what extent.

Again, can we see the connection? We have a VCXO that is usually powered by 3.3V - it needs power. The power we put into it has a noise content that can be defined spectrally.

The added jitter that comes out of the oscillator is directly proportional to the spectral content of the noise, analogue noise, not the digital content.

Hence, if we have Low Frequency noise (the worst kind), and the result is, the VCXO will add Low Frequency jitter. Higher frequency noise will add jitter content commensurate with that frequency. The analogue's spectral noise content is producing jitter of similar kind and frequency. It is as plain as that nose job on your face, analogue noise in, analogue jitter out. Jitter even has a frequency response! Again: Jitter is all analogue!

Harley is correct, the Esoteric Rubidium clock shows just how far we have fallen short, but this will not be the case much longer. The Atomic Clock’s superiority is as much due to the fact that the power supply dilemma demonstrated here is taken out of the equation. Now we come to the really good news. The Phoenix will rise from the ashes (trash can?), the VCXO will still emerge as everyman’s winner

Do You Need a Bottomless Pocket?

No, and emphatically so. I believe these are exciting time, while some say that CDs are in a decline, the fact remains that digital playback is here to stay even if it will be music servers (hard drive) based and not optical playback, and we may see the demise of the CD player. But even Music Servers will need to be clocked once the content is read into a live stream.

The best news of all is simply this. We do NOT need to spend Kilo bucks and that the humble VCXO now has a role to play in affordable playback that will scale heights that few have yet even to imagine.

Joe Rasmussen

At the Cross Roads

www.customanalogue.com

(Above article was published in the July issue of ASoN's Newsletter)

Terra Firma Player Upgrade Description

There are two version, Manual and Automatic. Currently, only Manual is available, but in sonic performance there is no difference. Terra Firma takes the technology developed by the Vacuum State team, sometimes referred to as the Reference Clock, to a new level. It was found that what was thought to be a previous limitation could be overcome by using a Delay technique. Waiting 12 hours before you could start playing the first CD or SACD hardly seemed a practical solution.

The delay switching can be done via a manual switch, but a relay can also be used using an electronic times delay. For now we will stay with the manual switch, especially when upgrading existing players, of which there are many hundreds.

The switch has two positions, Delay and Run . The first position is used when the player is freshly connected to the Mains supply. With newer players the delay will be 5 Minutes, then to the Run position. Now the player can be turned On and Off at will. The above only needs repeating if the Mains power supply is interrupted. Older players may need a longer Delay cycle and the user will be advised

.

This is the Terra Firma upgraded Oppo Multi-Player - note the toggle switch and the Delay and Run positions.

ADDENDUM:

Additional information and response to above will be posted here.

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Jitter is an instability in the timing of digital bits. It causes small changes in the audio waveform's shape, resulting in a sleight veiling of the sound (low level distortion). A jitter spec of 250 picoseconds is considered inaudible. Accurate A/D and D/A conversions rely on the clock precisely sampling the analog signal at equal time intervals. Any change between sampling the analog signal at equal time intervals. Any change between between the sampling time intervals. Any change between the sampling times, even nanoseconds, causes audible amplitude errors (distortion).

Jitter occurs during A/D and D/A conversion, but not during digital-to-digital copies. One cause of jitter is analog noise and crosstalk in the recording system. They affect the switching times and switching threshold of the clock, causing frequency modulation of the clock. They also affect analog filters and oscillators used in the clock's phase locked loops (PLLs). Jitter is also caused by inadequate digital cables. These cables pick up hum and noise, and introducing shift and high frequency attenuation, which degrade the timing of the digital signal.

To reduce jitter:

1. Use high quality clock sources with low jitter specs (under 1 nanosecond). Usually the internal clock in A/D and D/A Converter has less jitter than an external clock, such as AES/EBU or word clock.

2. Use high quality well- shielded digital cables and make them as short as possible.

3. Use the A/D convertor's internal clock as the master clock. Deed its AES or word-clock output to other slave devices in your studio to keep them in sync. If you use a separate word-clock cable, make it the same length as the digital audio cable.

Practical Recording Techniques  by Bruce Bartlett

Testimonial by Valther Baek-Hansen (Walter to his friends). His equipment:

RealTime Tube Preamp; Duntech Crown Prince Loudspeakers;Duntech Thor Sub;Turntable of my own design and built - NO thrust bearing but hydraulic thrust, 25 mm main shaft, hand lapped;Dynavector 505 modified bearings and dampening;Van den Hul cartridge modified by Mr. Van den Hul himself; Custom built Tube Power Amps running in Special Linear Triode Mode and fitted with LEM, the Transformer Permeability Booster Module:

I have over the past couple of years had upgrades done by Custom Analogue Audio's Joe Rasmussen, to my Sony SCD555ES CD/SACD Player, now up to Level 6 Vacuum State. Each time there has been a discernable improvement.

However, it has been the latest, the Terra Firma modification that has been the ultimate improvement.

This was evident after just a couple of bars of the first CD, not a Super Audio CD as I found when I checked. There was imaging that I have only heard on the very best analogue recording. The imaging was so wide and with such a depth in soundstage that I had to get another (unbiased) opinion – from my wife. She not only agreed with my findings but was impressed that she could understand words of a song in a language that she speaks only moderately well.

THIS IS DEFINITELY THE MOD OF ALL MODS.

Dare I say that maybe analogue may be just about redundant! Certainly only the best LPs, played on the very best of turntables, using the very best cartridges, run into something like a RealTime Tube Preamp, could hope to measure up to this ‘Terra Firma’ mod from Custom Analogue Audios Joe Rasmussen.

Valther Baek-Hansen.
 

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